Communication System And Communication Method

ABSTRACT

A communication system for providing access to a network via a second network to a wireless terminal on which an identification number for accessing a first network is stored, comprising: a receiving unit for receiving a connection initiation request on C-plane from the wireless terminal; a selection unit for selecting a gateway on U-plane to the network connected to the second network based on an obtained network ID of the second network, in response to the connection initiation request; and a sending unit for sending a gateway ID of the selected gateway on U-plane toward the second network.

TECHNICAL FIELD

The present invention relates to a communication system and acommunication method.

BACKGROUND ART

Along with a progress of globalization, the number of devices connectedto a computer network such as the Internet has increased, and the ideaof Internet of Things in which everything is networked is spreading.Hereinafter, a networked device is referred to as an “IoT device.” Thereare various network connection methods for IoT devices, but cases wherea cellular network is utilized are focused on herein.

It is also common that an IoT device connected to a network by acellular network is exported across a national border and, for example,a case can be considered in which a SIM card contracted with a Europeanmobile network operator (MNO) or a carrier is inserted into a product ina European factory and is imported into Japan.

When the IoT device attempts to access the computer network in Japan, anidentification number such as IMSI or ICCID is allocated to the SIMcard, and since information for specifying the aforementioned Europeancarrier which is the home location is associated with the identificationnumber, a connection initiation request to the computer network istransferred to the European carrier via the Japanese carrier which is ina mutual-connection relationship with the European carrier.

More specifically, as illustrated in FIG. 1, when a wireless terminal100 in which a SIM card contracted with a European carrier 110 isinserted is located in the area of a Japanese carrier 120 and initiatesaccessing an IP network 130, the wireless terminal 100 first sends aconnection initiation request including IMSI to a gateway (SGSN in 3G,and S-GW in LTE) (hereinafter referred to as a “visiting gateway” or a“visiting carrier gateway”) deployed in a core network of the Japanesecarrier 120 via a wireless base station which is an entry point of theJapanese carrier 120.

Upon receiving the connection initiation request, if the visitinggateway determines that an identification number is associated with theEuropean carrier 110 other than the Japanese carrier 120, the visitinggateway performs an authentication with the European carrier 110including presence or absence of a contract and the like based oninformation on the SIM card inserted in the wireless terminal 100, andthereafter DNS is referred based on the Access Point Name (APN) receivedfrom the wireless terminal 100 to obtain the IP address corresponding tothe APN. The IP address designates a gateway (GGSN in 3G, and P-GW inLTE) (hereinafter also referred to as a “home gateway” or a “homecarrier gateway”) which is an end point of a core network of theEuropean carrier 110, and the visiting gateway sends or transfers theconnection initiation request to the home gateway on a C-plane of atunneling protocol such as GTP via a network for providing aninter-carrier mutual connection such as GRX, and a tunnel is formedbetween the visiting gateway of the Japanese carrier 120 and the homegateway of the European carrier 110. Communication of the wirelessterminal 100 is transferred through the tunnel from the Japanese carrier120 to the European carrier 110, and transferred from the Europeancarrier 110 to an external IP network or the like.

SUMMARY OF INVENTION Technical Problem

Although it is possible to use a communication service within a servicearea of a partner carrier even outside a service area of a carrier thatissued the SIM card by an international roaming using an inter-carriermutual connection network such as GRX, an access must be made via a homelocation as illustrated in the example in FIG. 1. This causes delay ofdata communication due to increase in the communication distance, thenumber of network hops, etc. This is a so-called “triangle routing”problem.

A similar problem also occurs, for example, in a case where a SIM cardissued by a European carrier is inserted into an IoT device such as anin-vehicle device and used worldwide.

The present invention has been made in view of the aforementionedproblem, and a first objective of the present invention is to provide acommunication system or a communication method for providing an accessto a network via a second network (for example, the Japanese carrier) toa wireless terminal on which an identification number for accessing afirst network (for example, the European carrier) is stored (directly orindirectly), which can suppress a delay.

Further, a second objective of the present invention is to provide asecond network (for example, the Japanese carrier) or a communicationmethod by which an access to a network is provided to a wirelessterminal on which an identification number for accessing a first network(for example, the European carrier) is stored, which can suppress adelay.

Solution to Problem

To achieve the above objective, the first aspect of the presentinvention is a communication system for providing an access to a networkvia a second network to a wireless terminal on which an identificationnumber for accessing a first network is stored, comprising a receivingunit for receiving a connection initiation request on C-plane from thewireless terminal; a selection unit for selecting a gateway on U-planeto the network connected to the second network based on an obtainednetwork ID of the second network, in response to the connectioninitiation request; and a sending unit for sending a gateway ID of theselected gateway on U-plane toward the second network.

The second aspect of the present invention is the communication systemof the first aspect, wherein obtaining is performed by receiving thenetwork ID of the second network.

The third aspect of the present invention is the communication system ofthe second aspect, wherein the network ID is MCC and MNC.

The fourth aspect of the present invention is the communication systemof the second aspect, wherein the network ID is an IP address which is aU-plane destination included in a signaling from the second network.

The fifth aspect of the present invention is the communication system ofthe first aspect, wherein obtaining is performed by referring to aregistered network table stored on HLR/HSS based on the identificationnumber.

The sixth aspect of the present invention is the communication system ofany one of the first to fifth aspects, wherein the gateway on U-plane isselected by using a distance from a network with the network ID as acriterion based on the network ID.

The seventh aspect of the present invention is the communication systemof the sixth aspect, wherein the distance is an over-network distance.

The eighth aspect of the present invention is the communication systemof the sixth aspect, wherein the distance is a geographical distance.

The ninth aspect of the present invention is the communication system ofany one of the sixth to eighth aspects, wherein the gateway on U-planeis selected by referring to a gateway table retaining a correspondencebetween a plurality of network IDs and one or more gateways on U-planeassociated with a network with each network ID.

The tenth aspect of the present invention is the communication system ofany one of the first to ninth aspects, wherein the gateway on U-plane isselected based on the network ID and the identification number.

The eleventh aspect of the present invention is the communication systemof any one of the first to ninth aspects, wherein the gateway on U-planeis selected based only on the identification number.

The twelfth aspect of the present invention is the communication systemof any one of the first to eleventh aspects, wherein the gateway onU-plane is configured by one or more cloud instances.

The thirteenth aspect of the present invention is the communicationsystem of the twelfth aspect, wherein the gateway on U-plane does notshow a C-plane function when the wireless terminal accesses the networkvia the second network.

The fourteenth aspect of the present invention is the communicationsystem of any one of the first to thirteenth aspects, wherein the systemis configured by one or more cloud instances.

The fifteenth aspect of the invention is the communication system of anyone of the first to fourteenth aspects, wherein the system does not showa U-plane function when the system provides an access to the network viathe second network to the wireless terminal.

The sixteenth aspect of the present invention is the communicationsystem of any one of the first to fourteenth aspects, wherein the firstnetwork is a first MNO network, and wherein the second network is asecond MNO network other than the first MNO network.

The seventeenth aspect of the present invention is the communicationsystem of the sixteenth aspect, wherein one or more identificationnumbers are directly or indirectly stored on the wireless terminal, andwherein the identification number used when the wireless terminal sent aconnection initiation request is for accessing the first network.

The eighteenth aspect of the present invention the communication systemof the sixteenth or seventeenth aspect, wherein the identificationnumber is an IMSI.

The nineteenth aspect of the present invention the communication systemof any one of the sixteenth to eighteenth aspects, wherein the firstnetwork and the second network are mutually connected.

The twentieth aspect of the present invention the communication systemof any one of the sixteenth to nineteenth aspects, wherein the system isconnected to the first network via a mutual connection system.

The twenty-first aspect of the present invention the communicationsystem of any one of the first to twentieth aspects, wherein the sendingunit sends a generation request of a tunnel endpoint to the selectedgateway on U-plane.

The twenty-second aspect of the present invention is a communicationsystem for providing an access to a network via a visiting gateway to awireless terminal on which an identification number for accessing a homegateway is stored, comprising a receiving unit for receiving aconnection initiation request on C-plane from the wireless terminal; aselection unit for selecting a gateway on U-plane to the networkconnected to the visiting gateway based on an obtained network ID of thevisiting gateway, in response to the connection initiation request; anda sending unit for sending a gateway ID of the selected gateway onU-plane toward the visiting gateway.

The twenty-third aspect of the present invention is a communicationmethod for providing an access to a network via a second network to awireless terminal on which an identification number for accessing afirst network is stored, comprising the steps of receiving a connectioninitiation request on C-plane from the wireless terminal; selecting agateway on U-plane to the network connected to the second network basedon an obtained network ID of the second network, in response to theconnection initiation request; and sending a gateway ID of the selectedgateway on U-plane toward the second network.

The twenty-fourth aspect of the present invention is a program forcausing a computer to perform a communication method for providing anaccess to a network via a second network to a wireless terminal on whichan identification number for accessing a first network is stored, themethod comprising the steps of receiving a connection initiation requeston C-plane from the wireless terminal; selecting a gateway on U-plane tothe network connected to the second network based on an obtained networkID of the second network, in response to the connection initiationrequest; and sending a gateway ID of the selected gateway on U-planetoward the second network.

The twenty-fifth aspect of the present invention is a second networkwhich communicates with a communication system for providing an accessto a network via the second network to a wireless terminal on which anidentification number for accessing a first network is stored,comprising a receiving unit for receiving a connection initiationrequest on C-plane and an APN from the wireless terminal; and a sendingunit for sending the connection initiation request to the communicationsystem designated by an IP address determined by a DNS based on the APN,wherein a gateway ID of a selected gateway on U-plane to the networkconnected to the second network selected on the communication systembased on a network ID of the second network, in response to theconnection initiation request, is received, and wherein a communicationpath is established between the gateway on U-plane designated by thegateway ID.

The twenty-sixth aspect of the present invention is a communicationmethod to communicate with a communication system for providing anaccess to a network via a second network to a wireless terminal on whichan identification number for accessing a first network is stored,comprising the steps of receiving a connection initiation request onC-plane and an APN from the wireless terminal; sending the connectioninitiation request to the communication system designated by an IPaddress determined by a DNS based on the APN; receiving a gateway ID ofa selected gateway on U-plane to the network connected to the secondnetwork selected on the communication system based on a network ID ofthe second network, in response to the connection initiation request;and establishing a communication path between the gateway on U-planedesignated by the gateway ID.

The twenty-seventh aspect of the present is a program for causing acomputer to perform a communication method to communicate with acommunication system for providing an access to a network via a secondnetwork to a wireless terminal on which an identification number foraccessing a first network is stored, the method comprising the steps ofreceiving a connection initiation request on C-plane and an APN from thewireless terminal; sending the connection initiation request to thecommunication system designated by an IP address determined by a DNSbased on the APN; receiving a gateway ID of a selected gateway onU-plane to the network connected to the second network selected on thecommunication system based on a network ID of the second network, inresponse to the connection initiation request; and establishing acommunication path between the gateway on U-plane designated by thegateway ID.

Advantageous Effect of Invention

According to one aspect of the present invention, a gateway on U-planeconnected to a visiting gateway performing the C-plane function isselected based on a network ID of the visiting gateway, such that acommunication path is established between the gateways, whereby it ispossible to suppress delay due to passing through a home location.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a conventional international roaming.

FIG. 2 is a diagram illustrating a communication network including acommunication system according to one aspect of the present invention.

FIG. 3 is a diagram illustrating a signal flow in a communicationnetwork according to one aspect of the present invention.

FIG. 4 is a diagram illustrating details of a communication systemaccording to one aspect of the present invention.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present invention will be described indetail with reference to the drawings.

Outline of the Present Invention

FIG. 2 illustrates a communication network including a communicationsystem according to one embodiment of the present invention. For thesake of convenience, an example is explained in a case where a firstnetwork 210 is a network of a European carrier whose service area is apredetermined area in Europe, and a second network 220 is a network of aJapanese carrier whose service area is a predetermined area in Japan.The SIM card inserted in the wireless terminal 100 is contracted withthe European carrier in the same way as in FIG. 1, and the card holds anidentification number for accessing the European carrier.

Incidentally, two or more IMSIs may be stored in the SIM card insertedin the wireless terminal 100, and in addition to being stored in aphysical SIM card of the wireless terminal 100, one or a plurality ofIMSIs may be stored on a semiconductor chip (also referred to as “eSIM”)embedded in the wireless terminal 100 or one or the plurality of IMSIsmay be stored on a software installed in a secure area within a moduleof the wireless terminal 100, and various embodiments in which thewireless terminal 100 holds the identification number directly orindirectly may be considered.

Here, a communication system 200A is connected to a first network 210directly or via an inter-carrier mutual connection network such as GRX.With respect to the first network 210 which is an MNO, the communicationsystem 200A for providing a wireless communication service to an enduser by using its wireless communication infrastructure is located as apart of a network of a mobile virtual network operator (MVNO), andselects among a plurality of networks a third network 200B for formingof a tunnel by the wireless terminal 100 requesting an access to anetwork 130 such as an IP network, as will be described in detail below.Such a configuration can be said to have been made possible only aftertrying to operate the communication system 200A and the third network200B across a national border by the same operator, which is a novelidea that did not exist in the past.

In the following description, it is assumed that the communicationsystem 200A is a network separate from the first network 210, but it isnoted that the spirit of the present invention can also be applied, forexample, to a case where the communication system 200A is built as apart of the first network on the same network as the first network.

First, in order to access a computer network 130, the wireless terminal100 sends a connection initiation request to the second network 220(S301). Upon receiving the connection initiation request, the secondnetwork 220 determines whether the carrier associated with anidentification number, such as an IMSI included in the connectioninitiation request, is the second network 220 based on theidentification number. In a case where it is not the second network 220,that is, in a case where the second network 220 is a visiting gatewayfor the wireless terminal 100, presence or absence of a contract betweenthe first network 210 and the wireless terminal 100 (or the SIM cardinserted therein) is authenticated, and then an inquiry is made to a DNSwhich holds a correspondence between an APN received from the wirelessterminal 100 and an IP address of a gateway based on the APN (S302).Based on the received APN, the DNS sends an IP address of an accessdestination server corresponding to the APN to the second network 220(S303).

The DNS can be a part of the communication system 200A or can also bearranged at a position accessible from the communication system 200A orthe second network 220. For each APN, it is not necessary that one IPaddress correspond to the APN, but it is possible that a plurality of IPaddresses is made to correspond to the APN and an IP address can beallocated in a round robin manner when an APN is received or an IPaddress can be selected according to an identification number such asIMSI. Further, it is possible that, a network ID for identifying thesecond network 220 or the visiting gateway of the second network 220such as a mobile country code (MCC) and a mobile network code (MNC), anIP address, and the likes is received at the DNS and then the selectionis performed according to the network ID. More specifically, it ispossible to select a nearby one by using an over-network distance or ageographical distance from the second network 220 or the visitinggateway of the second network 220 specified by the network ID as acriterion. In a case where there is a plurality of IP addresses at thesame distance, one of them may be randomly selected.

Subsequently, the second network 220 sends, to the communication system200A or a server in the communication system 200A designated by the IPaddress corresponding to the APN, the connection initiation request (inthe present specification, the “connection initiation request” alsoincludes a request sent by the second network 220 which substantiallycorresponding to the connection initiation request received by thesecond network 220) or an identification number included in theconnection initiation request, and a network ID for identifying thesecond network 220 (S304). Specifically, an ID of the gateway of thesecond network 220, such as a mobile country code (MCC) and a mobilenetwork code (MNC), an IP address, or the likes can be used as thenetwork ID. In a signaling on C-plane sent from the second network 220,an IP address of the second network 220 or the visiting gateway of thesecond network 220 is included as a U-plane destination, and this can beused as the network ID.

In addition to the network ID, the second network 220 may further sendauxiliary information for assisting the communication system 200A inselecting a gateway or a third network 200B including the gateway forthe wireless terminal 100 to establish a connection, to thecommunication system 200A.

The communication system 200A stores a gateway table that retains acorrespondence between a network ID and a gateway on U-plane associatedwith the network with the network ID, and based on the received networkID, the wireless terminal 100 can select the gateway or the thirdnetwork 200B including the gateway for the wireless terminal 100 toestablish the connection. In addition, in response to the receivedconnection initiation request, the communication system 200A also makesa request to generate a tunnel end point (TE) ID to the selected thirdnetwork 200B or the gateway thereof as necessary (S305).

The communication system 200A receives an ID of the tunnel end point(TEID) from the third network 200B (S306), and sends the same togetherwith the gateway ID to the second network 220 (S307). The gateway ID is,for example, an IP address of a selected gateway on U-plane. In a casewhere the gateway of the third network 200B has two or more serversconnectable to the second network 220, an IP address of any one of themis selected as the gateway ID.

Upon receiving the gateway ID and the TEID, the second network 220 formsa tunnel between the visiting gateway of the second network 220 and thegateway of the third network 200B designated by the gateway ID (S308).

In the conventional international roaming, it is always required toreturn to the first network 210 that is a home carrier to performcommunication, which causes a delay, but according to the presentinvention, the wireless terminal 100 can form a tunnel on U-planebetween itself and the gateway of the third network 200B associated withthe second network 220 that is the visiting carrier, and the homelocation can be shortcut to improve the delay remarkably.

Incidentally, an example of an access destination network by thewireless terminal 100 is not only an IP network such as the Internet butalso a non-IP network. In addition to a public system, a private systemmay also be mentioned. In addition to an on-premises private system, ina case where at least a part of the third network 200B is realized onthe cloud, the private system includes a different IP network on thesame cloud, an IP network on a different cloud, or the like, and theseprivate systems and the third network 200B may be connected to eachother by a dedicated line or a virtual dedicated line.

(Details of Communication System)

FIG. 4 illustrates details of a server included in a communicationsystem according to one embodiment of the present invention. Each of oneor a plurality of servers 400 included in the communication system 200Acan be a server including a communication unit 401 such as acommunication interface that receives a connection initiation request onC-plane from the wireless terminal 100 and a processing unit 403 such asa CPU that selects a gateway to the computer network 130 connected tothe second network 220 by referring to the gateway table stored in astorage unit 402 such as a memory and a hard disk based on the obtainednetwork ID of the second network 220 in response to the connectioninitiation request. The communication unit 401 sends the gateway ID ofthe selected gateway to the second network 220. If the ID of a tunnelend point generated by the selected gateway has been received, thecommunication unit 401 also sends the same to the second network 220.

The server is not limited to a single physical server but can also be aplurality of accessible servers, and the storage unit 402 may be astorage device accessible from the server on the computer network. Inaddition, an operation in one or both of the communication unit 401 andthe processing unit 403 can be realized by executing one or a pluralityof programs to cause the computer to perform the pertinent operation.

The server 400 may be an instance on a public cloud or a private cloud.Here, in the present specification, the term “cloud” refers to a systemcapable of dynamically provisioning and providing computing resourcessuch as a CPU, a memory, a storage, and a network bandwidth according todemand on a network. For example, the cloud can be used by AWS or thelike.

In order to provide an access to the network 130 via the second network220 to the wireless terminal 100, the communication system 200A can beconfigured to perform a C-plane function when initiating the connectionand not perform a U-plane function. The U-plane function can beperformed in the third network 200B whose service area is outsidea_service area or outside an area of one or both of the first network210 and the communication system 200A, such as abroad. In a case wherethe third network 200B is outside the service area or outside the areaof the communication system 200A, it does not necessarily mean that thethird network 200B is abroad with respect to the communication system200A. The third network 200B can perform a U-plane function whenproviding the access to the computer network 130 via the second network220 to the wireless terminal 100, but it can be configured not toperform a C-plane function.

(Details of Gateway Table)

The gateway table that can be held or accessed by the communicationsystem 200A determines a correspondence relationship between a networkID and a gateway or server associated with the network with the networkID or the network including the gateway.

In one aspect, the gateway table determines a correspondencerelationship between a network ID, such as an IP address, and one or aplurality of gateways or a network (that is, the third network 200B)including the gateways that are located in the vicinity of a network(that is, the second network 220) with the network ID or its gatewayamong the scattered networks or gateways. Here, a “distance” to thegateway can be an over-network distance measured by delay time. Theover-network distance can be calculated by, for example, the number ofhops. Further, it can be considered that geographically close gatewaysare located in the vicinity in that order.

Further, in another embodiment, it is also possible to determine acorrespondence relationship between a network ID and one or a pluralityof gateways outside the service area of the network (that is, the secondnetwork 220) with the network ID or a network including the gateways.

Further, for example, it is also possible to associate a plurality ofgateways or a network including the gateways with one network ID, anddetermine which gateway is in charge in accordance with anidentification number such as IMSI included in the connection initiationrequest. Then, with respect to a specific identification number, it ispossible to associate a gateway for which a specific service on U-planeis available or a network including the gateway regardless of thedistance, and for example, it is possible to select the gateway onU-plane based only on the identification number.

Further, at the communication system 200A or the server accessible fromthe communication system 200A, metrics of a processing capability ofeach of a plurality of U-plane gateways associated with the secondnetwork 220 may be monitored, and the gateway with a lower processingload may be selected. Examples of the metrics to be monitored includeCPU load, memory utilization rate, disk read, disk write, amount ofreceiving network traffic, amount of sending network traffic, and thelike. One or a plurality of servers of each gateway associated with thesecond network 220 can be instances on the public cloud or privatecloud. In the selection of the gateway on U-plane by using the distancedescribed above as a criterion, it is also advantageous to finallyselect the one with the lower processing load when there is a pluralityof equivalent gateways.

Further, in another embodiment, the communication system 200A mayreceive the auxiliary information from the second network 220. As aspecific example, there may be one or a plurality of servers serving asoutlets for a connection between the second network 220 and the thirdnetwork 200B, and an IP address of each server may be received as theauxiliary information. In this case, in the communication system 200A, agateway of a connection destination or the third network 200B includingthe gateway may be selected by using each server as the basis, and acombination of the shortest distance between the second network 220 andthe third network 200B may be selected. It is also possible to regardthe IP address of each server as a network ID and to interpret that aplurality of network IDs are being received by the communication system200A.

(HLR/HSS)

Regarding the network ID of the second network 220, the mobile countrycode (MCC) and the mobile network code (MNC), the IP address that is theU-plane destination included in the signaling on C-plane, or the likesare exemplified in the above description, but it is also possible forthe communication system 200A to refer to HLR/HSS or subscriberinformation management database based on the identification number suchas IMSI to obtain a network ID such as an IP address of a visitinggateway or the second network 220 including the same as a registerednetwork of the wireless terminal 100. More specifically, in the HLR/HSSor the subscriber information management database, it is possible that aregistered network table retaining the registered network where eachwireless terminal exists is stored and a network ID such as the mobilecountry code (MCC) and the mobile network code (MNC), or the likes canbe determined by referring to the table.

(Details of Second Network)

Like the communication system 200A, the second network 220 includes oneor a plurality of servers, each of which includes a communication unitsuch as a communication interface, a storage unit such as a memory and ahard disk, and a processing unit such as a CPU, performs sending and/orreceiving of the data in the communication unit, and performs requiredprocessing in the processing unit. The storage unit may be a storagedevice that can be accessed from the server on the computer network, andan operation in one or both of the communication unit and the processingunit can be realized by executing one or a plurality of programs forcausing the computer to perform the pertinent operation. Further, one orthe plurality of servers of the second network 220 can be instances on apublic cloud or a private cloud.

REFERENCE SIGNS LIST

-   -   100 WIRELESS TERMINAL    -   110 EUROPEAN CARRIER    -   120 JAPANESE CARRIER    -   130 IP NETWORK    -   200A COMMUNICATION SYSTEM    -   200B THIRD NETWORK    -   210 FIRST NETWORK    -   220 SECOND NETWORK    -   400 SERVER    -   401 COMMUNICATION UNIT    -   402 STORAGE UNIT    -   403 PROCESSING UNIT

1. A communication system for providing an access to a network via asecond network to a wireless terminal on which an identification numberfor accessing a first network is stored, comprising: a receiving unitfor receiving a connection initiation request on C-plane from thewireless terminal; a selection unit for selecting a gateway on U-planeto the network connected to the second network based on an obtainednetwork ID of the second network, in response to the connectioninitiation request; and a sending unit for sending a gateway ID of theselected gateway on U-plane toward the second network.
 2. Thecommunication system according to claim 1, wherein obtaining isperformed by receiving the network ID of the second network.
 3. Thecommunication system according to claim 2, wherein the network ID is MCCand MNC.
 4. The communication system according to claim 2, wherein thenetwork ID is an IP address which is a U-plane destination included in asignaling from the second network.
 5. The communication system accordingto claim 1, wherein obtaining is performed by referring to a registerednetwork table stored on HLR/HSS based on the identification number. 6.The communication system according to claim 1, wherein the gateway onU-plane is selected by using a distance from a network with the networkID as a criterion based on the network ID.
 7. The communication systemaccording to claim 6, wherein the distance is an over-network distance.8. The communication system according to claim 6, wherein the distanceis a geographical distance.
 9. The communication system according toclaim 6, wherein the gateway on U-plane is selected by referring tocorrespondence between a plurality of network IDs and one or moregateways on U-plane associated with a network with each network ID. 10.The communication system according to claim 1, wherein the gateway onU-plane is selected based only on the identification number.
 11. Thecommunication system according to claim 1, wherein the gateway onU-plane is configured by one or more cloud instances.
 12. Thecommunication system according claim 11, wherein the gateway on U-planedoes not show a C-plane function when the wireless terminal accesses thenetwork via the second network.
 13. The communication system accordingto claim 1, wherein the system is configured by one or more cloudinstances.
 14. The communication system according to claim 1, whereinthe system does not show a U-plane function when the system provides anaccess to the network via the second network to the wireless terminal.15. A communication system for providing an access to a network via avisiting gateway to a wireless terminal on which an identificationnumber for accessing a home gateway is stored, comprising: a receivingunit for receiving a connection initiation request on C-plane from thewireless terminal; a selection unit for selecting a gateway on U-planeto the network connected to the visiting gateway based on an obtainednetwork ID of the visiting gateway, in response to the connectioninitiation request; and a sending unit for sending a gateway ID of theselected gateway on U-plane toward the visiting gateway.
 16. Acommunication method for providing an access to a network via a secondnetwork to a wireless terminal on which an identification number foraccessing a first network is stored, comprising the steps of: receivinga connection initiation request on C-plane from the wireless terminal;selecting a gateway on U-plane to the network connected to the secondnetwork based on an obtained network ID of the second network, inresponse to the connection initiation request; and sending a gateway IDof the selected gateway on U-plane toward the second network.
 17. Aprogram for causing a computer to perform a communication method forproviding an access to a network via a second network to a wirelessterminal on which an identification number for accessing a first networkis stored, the method comprising the steps of: receiving a connectioninitiation request on C-plane from the wireless terminal; selecting agateway on U-plane to the network connected to the second network basedon an obtained network ID of the second network, in response to theconnection initiation request; and sending a gateway ID of the selectedgateway on U-plane toward the second network.
 18. A second network whichcommunicates with a communication system for providing an access to anetwork via the second network to a wireless terminal on which anidentification number for accessing a first network is stored,comprising: a receiving unit for receiving a connection initiationrequest on C-plane and an APN from the wireless terminal; and a sendingunit for sending the connection initiation request to the communicationsystem designated by an IP address determined by a DNS based on the APN,wherein a gateway ID of a selected gateway on U-plane to the networkconnected to the second network selected on the communication systembased on a network ID of the second network, in response to theconnection initiation request, is received, and wherein a communicationpath is established between the gateway on U-plane designated by thegateway ID.
 19. A communication method to communicate with acommunication system for providing an access to a network via a secondnetwork to a wireless terminal on which an identification number foraccessing a first network is stored, comprising the steps of: receivinga connection initiation request on C-plane and an APN from the wirelessterminal; sending the connection initiation request to the communicationsystem designated by an IP address determined by a DNS based on the APN;receiving a gateway ID of a selected gateway on U-plane to the networkconnected to the second network selected on the communication systembased on a network ID of the second network, in response to theconnection initiation request; and establishing a communication pathbetween the gateway on U-plane designated by the gateway ID.
 20. Aprogram for causing a computer to perform a communication method tocommunicate with a communication system for providing an access to anetwork via a second network to a wireless terminal on which anidentification number for accessing a first network is stored, themethod comprising the steps of: receiving a connection initiationrequest on C-plane and an APN from the wireless terminal; sending theconnection initiation request to the communication system designated byan IP address determined by a DNS based on the APN; receiving a gatewayID of a selected gateway on U-plane to the network connected to thesecond network selected on the communication system based on a networkID of the second network, in response to the connection initiationrequest; and establishing a communication path between the gateway onU-plane designated by the gateway ID.